Louiza T. Dimowa

A microporous titanosilicate for selective killing of HeLa cancer cells

Structural distribution of zinc(II) ions in the pore system of three silicate molecular sieves has revealed an unprecedented application of the microporous titanosilicate Zn–ETS-4 as a non toxic, highly efficient and selective inhibitor of HeLa cancer cells.

Measurement of nonlinear refractive index and multiphoton absorption by the subpicosecond z-scan method of tellurite multicomponent glassy matrixes having nonlinear susceptibility

Abstract New multicomponent tellurite glassy matrixes possessing high nonlinear susceptibility weredeveloped and their optical properties were studied. The nonlinear refractive index n 2 andmultiphoton absorption β were measured by using the subpicosecond z -scan method.Second-harmonic generation was observed in poled glassy samples.PACS numbers: 61.43.−j, 42.70.Ce, 42.65.Re, 42.65.Ky(Some figures may appear in color only in the online journal) 1. Introduction Vigorousinvestigationsofpoledglasseshavebeencarriedoutsince the observation of unusually efficient second-harmonicgeneration (SHG) in germanium–silica glass fibers [1] andthermally–electrically poled [2] fused silica glasses. Thereason for the intensive studies of such disordered materialsand related centrosymmetrical crystals is the ability to changetheir nonlinear optical susceptibility by poling (optical,thermal, electrical, etc). This phenomenon could be usedin optical memory storage, optic switching and some otheroptical communication applications [3, 4].The poling of glasses and centrosymmetrical crystals isbased on breaking of the macroscopic matrix symmetry. Theobtained deformations range in size from several nanometerstomicrometers.Themainadvantageofglassescomparedwithsingle crystals and polycrystalline materials is the possibilityof obtaining samples with the desired shape (almost anyshape). Additionally, glasses possess high transparency in abroad wavelength range and their poling may be achievedrelatively easily when compared with that applied to singlecrystals.Tellurite glasses are promising materials for lasertechnologybecauseoftheirextendedvisibleandinfrared(IR)transmission range as well as their high refractive linear andnonlinearindices[5,6],andamongoxideglassestheypossessone of the highest third-order nonlinear susceptibilities [7].Moreover, they are relatively easily producible due to theirrelatively low melting temperatures. Tellurite glasses withheavy metal oxides were found to show remarkable physicaland optical properties [8–12].SHG in thermally assisted electro-poled tellurite glassmatrixes was reported in [10, 13–14]. Sum frequencygeneration in poled glassy matrixes was reported by Fujii

Structural study of Zn-exchanged natural clinoptilolite using powder XRD and positron annihilation data

Abstract Zn-exchanged natural clinoptilolite was studied by powder X-ray diffraction and positron annihilation lifetime spectroscopy. The original clinoptilolite tuff was subjected to size fractionation by sedimentation and dissolution of cristobalite (opal-C). After Zn2+-exchange the purified clinoptilolite sample contained 2.2 Zn2+ ions per unit cell. Structural details obtained by Rietveld refinement showed that the Zn2+ cations are located in three sites (Zn1, Zn2 and Zn3) in the channels of the clinoptilolite. Site Zn1 is located in the centre of channel-A (Mg2+-M4 site). Site Zn2 is in channel-B, next to the calcium M2 position. A new Zn3 site is located in channel-A, in imminent proximity to Zn1. Positron Annihilation Lifetime Spectroscopy (PALS) was employed to assess the Zn exchange. As the cation content influences the free volume of the channels, the ion-exchange process can be monitored by PALS. The results suggest the existence of two sizes of cavities, in accordance with the structural refinement.

Synthesis of MOFs from Zn,Cd,Ni-4-carboxyphenylboronic acid with DMF solvent

Synthesis and characterization of porous metal organic frameworks (MOFs) has prompted considerable interest because of the possibility to design the pore size and physical/chemical properties by suitable selection of the organic linkers (ligands). In this work, we have chosen a classical solvothermal synthesis strategy involving 4-carboxyphenylboronic acid, a molecule that is analogic to the terephthalic acid, ZnCdNi-OAc metal salts and DMF as solvent. It is known that during solvothermal synthesis DMF decomposes to dimethylamine which is easily incorporated in MOF’s [1], [2]. The obtained MOFs are characterized by single-crystal X-ray diffraction, X-ray powder diffraction, TG analyses, IR spectroscopy and BET analyses. Preliminary X-ray single crystal diffraction results showed that a new type of structure may be produced in function of the temperature. The Cdstructure crystalizes in the hexagonal Space group P6222, with respective parameters of a = 14.4113(12), c = 13.0416(7) Å (Fig. 1). The cadmium ion is tetra coordinated by the oxygens of the B(OH)2 and COOmoieties. The 4-carboxyphenylboronic acid is disorder and attempts to lower the symmetry to model the disorder resulted in unstable refinement. In the studied systems in addition to the reported new compound isotypical structures to MOF-5 containing 4-carboxyphenylboronic acid instead of 1,4-benzenedicarboxylate were also obtained.